Batteryless radiation indicator



FIPBlO June 21, 1960 l n LEHovEc AmYLsss RADIATION INDICATOR 'Filed uarcn s. 19,55

' SUB'IITUTE FCR MISSING XR Fx e,

- SMU/WIC RADIATION SEA/SER SUSATOM/C United States Patent Cllce j www i' is etcient 'uid at the same time snall, easy to manage.

. invention; and

' atomic radiation indicator emboc's-.g the present invention.

cell. has output leads i2. 13 contested to the input terminals of a transistor 16. 'I'ne uansistor's output leads ss little as one. milliaaipere at a potential of about one volt or even less. An ordinaire-.Econ type cell such as Y Appl. Phys. 25, 676 (i954), will be suitable.

v lead is common to. its input ari output.

l 2,942,110 Patented June 21, 1960 Y BATTERYLESS RADIATIGN INDICATGR Kurt Lehovec, South Will'a' Mas., assigner in Sprague Electric Company, Nora Adams, Mms., a corporation of Massachusetts Fried Mar. 9,1955, Ser. No. 493,095

`s claim (er. :se-ssa) of radioactive material.

Among the cbjects of the pt rr.: invention is the provision of a baterylesr indicator of the above type which and does Let l:al for maintenance.

The above as well as asitica-si objects of the present exemplltications, ref- Pigj'l is a schematic diagram showing one form o a. subatomic radiation indicator according to the present Pig. 2 is a similar showing of a modified form of. sub- .Y 4This invention relates s'net-.cC-.ic radiation indicators 15 such as those that can be used to indicate the presence?.

Semiconductor barrier lag-*er oeils Suche: those discusscd in an article by P. Rzpptpmt, Phys. Rev. 93, 246

A (1954), entitled The Electron-'Veins Btcct in p-n junctions Induced by Beta-Paride Bombardrnent, will respond to subatorric radiation, as beta rays, by the generation of a minute electric errent. This gereration takes place .tie absence of external power supplies. Unfortunately` '.l' amount cf errent generated in this way is usualty of the order of en: microampere. Al-

sirnpie meters of the kind that are portable, light, cornby simple meters introduces fur-.':er dilhculties.

Accor-.ling to the present inversion, a very convenient form of indicator of the alc-ove type is provided by a d semiconductor barrier layer cell leaving a transistor com uected to amplify its current, the transistor in turn being powered by a power-.l-.zrpplying nansducer that is energized by low frequency radiation sach as ordinary illumination or body beat.

Referring to ig. l, a sncatocc radiation senser 10, which can be a conventional semiconductor barrier layer 18, i9 are in turn connected th. agit a current measuring meter 22 to a photovoltaic cell 24. The cell is exposed to .ambient light such as ordinary daylight and can supply that described in th: letter by srrnerow, Phys. Rev. 9S. 561 1954), and the D. Chapin et al. letter of the J.

The transistor 16 is sbo ysr.: as mnnected in a socalled grounded emitter amplifying circuit, that is, its emitter With this ar-V al as loe. as one volt will actuate the a ore ntixrmmpere current by as muc 'u as 5U to 50 tintes or more. Inasmuch as standard i metzzrs 22 are available relatively small., rugged sizes 40 l though it is possiole to measure sich minute currents.

to measure as little as 25 microamperes, Fig. 1 represents a very practical combination. By merely arranging the components in a suitable container so that the senser 10 is exposed to subatomic radiation while cell 24 is exposed to daylight, the meter 22 will conveniently indicate subatorric radiation and the entire apparatus will be relatively small and light in weight. The transistor and photovolraic cell themselves will take up only about one cubic indi of space, and their combined weight will only be n few grams. The meters 22 can weigh as little as V4 pound and can be tted into a space of less than l0 cubic inches. 1

In accordance with the standard practice, it is sometimes helpful to insert a biasing resistor in the emitter return connection to stabii'nte the amplication. This resistor need be only about 400 ohms, and is desirably bypassed by s capacitance of up to several microt'arads in order to minimize the degenerative el'ects of the resistor on the amplihcation.

Ii desired. the combination can be arranged to provide an aural indication of subatomic radiation as by having the meter of the standard DArscnval type with a pointer that is actuated by the amplied current, and astop which the pointer will strike when it is actuated through a :ucient amplitude. In striking this stop, the pointer will generare a distinct tick-like sound which is easily heard. Where the amplification is arranged to provide currents larger than the measuring range of the meter, the standard upper limit stop for the pointer will provide the sound without rcrniring a modcation of the meter. To im crease the intensity of the sound, the stop can be arranged to provide a metal-to tftetal engagement when hit by the moving pointer. Furthermore, the meter can be carried on che head or around tlf.: neck so that the sound would be ,'eneratei close to the ear while the remainder of the apparatus can be connected at the end of a cable so that it can be conveniently held close to the ground or some object to be particularly tested.

Although a point-contact transistor can be used, ford best rfsults a junction transistor is desirable inasmuch as the :t-.rent amplification of junction transistors, either of the l-fpN or p-N-p type is much larger than that of poen-contact transistors. The amplicd current output is relatively insensitive to changes of actuating potential as long as this potential is above a minimum of about l volt. The combination will accordingly be able to provide a ffir closely reproducible meter operan'on even though the Lght intensity is subject to wide variation. The gmundxd or common emitter type of connection is preferred since it generally provides the maximum degree of amplication with either point-contact or junction transistors. p-N-p-N junction transistors are also suit able for use in the combination of Fig. l.

Fig. 2 shows a combination similar to Fig. l except that a thermocouple 30 is used instead of a photovoltaic cell, to provide the transistor operating power. By using a thermocouple having a plurality of series-connected cold and hot junctions, particularly with thermocouple pairs, auch as germanium and lead or silicon and lead, that provide a relatively high voltage output per junction. an output power of several volts sucicnt to deliver a few milliamperes of current is readily obtained. The cold and hot junctions should bc separated from each other and all the hot junctions collected in one piace so that the collection can be conveniently held against a persons y while the cold junctions are exposed zo the outside temperature. The hot junctions can, for example, be arranged to be inserted under an armpit while the cold junctions are carried with the meter around the neck or or, the head. The hot junctions can in this way be kept very close to the 37' .C. normal body temperature sunshine. or hot summer daytime temperatures, usually be maintained at leest about l to 20 degne colder.

An acvaotcge of the thermoconple power system of Fig.

2 is that it does not need any appreclc amount of drylight for its operation. pnrticnleriy trhere aural. signals are to be used rather than the v cal reading of the meter.v A very desirable form of tbe invwion can, for example` to enable the Lnermoeonpie to provide good power.

Tite sintomi.: radiation senser is not restricted to being .a semi-conductor barrier :zeil` as indicated above,

but can be any other type of cell that is capable of generasing a small current when any radioactive radiation euch es alpha, beta, gamma or neutron rays impinge upon it. Titus a photon-ansistor can be 1sed for this purpose.

f Such a pilotctransistor can for example be a body of germanium or silicon with a p-N junction exposed to radiation and electrically `biased 'm the current-bloclting direction. Tis: impigement of radiation lowers the blc-:Ising eect of the barrier junction and permits an eppreciabe amount of currentto pass. The low-fre queney-mdictioncnergized transducer of Figs. 1 or 2 can be used to efieet the biasing as well as any amplification Y that is desired. Also with a phototransistor considerable change of current accompanies minor changes of radiation, hence the radiation transducer and amplier are combined into one element. For best results, the phototransistor should be made insensitive to other radiation that could mais the subetornic radiation. By way of example, the exposed junction can be covered with a light-impermeable material through which gamma rays or the like will readily pass. A thin sheet of metal or a paint layer'will be satisfactory. Low atomic weight materials, such as aluminum, are particularly desirable since they will oiier the least resistance to radioactive radiation while still preventing any iight transmission.

As many apparently widely diilerent embodiments of this invention may be made without departing from the spirit and scope hereof, it is xo bc understood that the invention is no: limited to the specific embodiments hereof except :s defined in the appended claims.

l. A batzeryless atomic radiation indicator having a semiconductor barrier layer cell that spontaneously gcnerates a minute electrical current Vwhen it receives atomic radiation, a transistor connected to said cell to amplify the generated current, a power-supplying transducer energized by low-frequency radiation connected tn power the transistor amplification and cause it to supply electric current of appreciable magnitude, and acurrent indicating device connected to indicate the amplified current.

2. The invention of claim l in which the poner-suppl ing transducer is a photovoltaic cell.

ing transducer is a thermocouple.

4. The invention of claim l in which the transistor is a junction type transistor and is connected to protdde l grounded emitter amplifying circuit.

5. A batteryless atomic radiation indicator having a phototransistor exposed to any incidence of atomic radiation, a power-supplying photovoltaic cell energized by visible light connected to bias said phototransistor in the current blocking direction and a current indicaiing device connected to the output cf said photo-transistor to indicate any variation of incident atomic radiation.

References cned in the sie of mi pmmr muren STATES PArt-:Nts

2,375,130 Perrin et al. May l. X945 2,579,336 Rack Dec. 18. i 2,579,994 Zinn Dec. 25, 1951 2,582,850 Rose Jan. l5, 1952 I 2,588,254 ,Lark-Horwitz Mar. 4. 1952 2,622.117 Benzer Dec. 16. 1952 2,696,564 Ohmart De". 7, 1954 by Gernsbach Pub. Inc., 1954, pages 96. and 97. 

